95 YJ 4 cyl rough idle/cutting out

hester88 · 04-23-2012, 08:09 AM

So here lately my jeep has started running like Crap. It idles really rough almost dieing then coming back up. And also starts missing when it gets over 2 grand. I've looked at some of the threads started about problems similar but they just die and never say what fixed them or if anything ever did fix it.

I've replaced these:

Distributer cap, stator, and rotor.
Ignition coil.
Spark plugs and wires.
Crankshaft position sensor.
Fuel filter.
Air filter.
And an injector that was bad.

I have checked:

Timing with a timing light.
Spark on all plugs.
Drained fuel to about 1/8th tank, added heet and seafoam then filled back up with fresh gas.
Pulled MAP sensor while running and it falls on its face.

Haven't got ahold of a compression tester yet that will fit and haven't got ahold of a fuel pressure gauge.

I also have either a collapsed lifter or bent intake valve. But I don't know if that would cause my problems or not. I'm about out of ideas and it's starting to get expensive throwing parts at it. Any suggestions would be great. Thanks.

**Que89YJ** · 04-23-2012, 09:13 AM

Hester if you are sure you have a bent valve/lifter or a bad rocker then yes it can cause the issue. It will throw the air fuel out to lunch at the O2 sensor.

Run the diagnostics and see if you have any faults:
http://www.jeepforum.com/forum/f12/h...codes-1257145/

The IAC is another possiblity. It need to be cleaned evry now and then:
http://www.jeepforum.com/forum/f12/q...-body-1262267/

If you post back and don't hear from me, pm me. The automatic response email is not working the greatest.

hester88 · 04-23-2012, 10:13 AM

I checked for codes doing the key trick. Nothing showed up. No check engine light either. Pulled a couple plugs off sensors to get it to fault to make sure the check engine light worked and it does. Also, don't think my jeep has the iac valve. It's multi port injection instead of tbi. Might be wrong but ill have to double check the repair manual after work today. By the way, we had the valve cover off looking at that valve and the rocker is loose on cyl 1 intake. We swapped rockers, reversed the bridge, and swapped push rods and the intake always stayed loose. Leads me to believe it'd be a collapsed lifter or bent valve not seating all the way.

Edit:
Just got the pics to load on that link and seen the iac you are talking about. I'll take it off when I get home and clean it.

**Que89YJ** · 04-23-2012, 11:04 AM

The CEL did not light at all? It sounds like a lifter is bad. The good and bad of it is that the 2.5L you are suppose the lifters with a puller but if you find a warn lifter and not just a colapsed lifter then you really need to replace the cam and all the lifters. If the lifters are warn the cam lobe will be too.

hester88 · 04-23-2012, 11:06 AM

How hard are they to change?

hester88 · 04-23-2012, 05:13 PM

Cleaned the iac and reset the ecu (forgot to after replacing the injector) ran like a champ till it got warmed up. Then started cutting out and would die when it came down to idle. Starting to sound like the same problem now that the other guy had in the other thread. Gonna go back over what you told him to do and check some sensors.

pete1991YJ · 04-23-2012, 06:09 PM

Get a new cam and lifters. Que nailed it, IMHO. Its not much harder than doing a water pump. You have to pay real close attention to the mechanical timing tho (relation ship between cam and crank) Any good manual will have that info.

hester88 · 04-23-2012, 06:19 PM

Ok. Thanks. Just messed with it some more and pulled the injector off that I replaced on cyl 3 and still no change in idle. Pulled cyl 1,2, and 4 off and it almost dies. Changed spark plug to make sure it wasn't fouled and same thing. I get a code now for fuel injector control when I pull the injector plug off. By the way, cyl 1 is the one with the lifter problem.

**Que89YJ** · 04-24-2012, 07:47 PM

You are going to have to deal with the mechanical issue before moving on to anything else. The fact is the mechanical issue would change the exhaust and impact your O2 sensor readings. That means when you are warmed and going into closed loop the O2 is changing in response to it.

pete1991YJ · 04-24-2012, 07:53 PM

Quote:

Originally Posted by Que89YJ

You are going to have to deal with the mechanical issue before moving on to anything else. The fact is the mechanical issue would change the exhaust and impact your O2 sensor readings. That means when you are warmed and going into closed loop the O2 is changing in response to it.

^^^^ X2 get the mechanicals fixed first before you even think about the electrics and sensors. Jacking round with the sensors right now won't accomlish anything.
.

hester88 · 04-24-2012, 08:13 PM

Alright. Hopefully its just the lifter and not the valve bent. I just checked the o2 sensor also from how you was telling that other guy and it was alternating between .2v and .6v. Also, earlier I mentioned cyl 3 acting dead. If that valve is messing with my emissions why would it effect cyl 3 and not cyl 1 where the problem is? Or any of the other cylinders?

pete1991YJ · 04-24-2012, 08:22 PM

Quote:

Originally Posted by hester88

Alright. Hopefully its just the lifter and not the valve bent. I just checked the o2 sensor also from how you was telling that other guy and it was alternating between .2v and .6v. Also, earlier I mentioned cyl 3 acting dead. If that valve is messing with my emissions why would it effect cyl 3 and not cyl 1 where the problem is? Or any of the other cylinders?

I think whats happening is you got 2 problems on 2 different cyls, and not just one. Cyl 3 was the one where you pulled the wire it didn't make any difference right? Thats prolly a sensor electrical prob. But cyl 1 is the one with the lifter/valve prob right? that's definitely mechanical. Basically its only running on 2-1/2 cyls. prolly. Look at the O2 volts. its in range but a tad on the lean side. That would mean its pulling a bunch of raw air, prolly a valve stuck "open" or its gummed up and moving too slow to close tight. Only other thing it would be is a manifold leak.

hester88 · 04-24-2012, 08:53 PM

Quote:

Originally Posted by pete1991YJ

I think whats happening is you got 2 problems on 2 different cyls, and not just one. Cyl 3 was the one where you pulled the wire it didn't make any difference right? Thats prolly a sensor electrical prob. But cyl 1 is the one with the lifter/valve prob right? that's definitely mechanical. Basically its only running on 2-1/2 cyls. prolly. Look at the O2 volts. its in range but a tad on the lean side. That would mean its pulling a bunch of raw air, prolly a valve stuck "open" or its gummed up and moving too slow to close tight. Only other thing it would be is a manifold leak.

You are correct on the cylinders. We sprayed around intake and didn't seem like it was leaking anywhere. If that intake valve is bent that would cause it to run lean. As far as cyl 3 acting dead not really sure. Has plenty of spark and a new injector. Has power at the plug. I don't know if I mentioned this earlier but since changing the injector it idles fine until it warms up then starts messing up. And that's when that cyl 3 acts dead. If I start it up while it's cold and idling fine and pull the plug would that tell me that cyl is fine if it messes up the idle?

pete1991YJ · 04-24-2012, 09:27 PM

OK let me see if I got this right.

Yeah on the mechanical probs - you are going to have to do those first.

The #3 injector, you replaced it with a known good one. But it only acts dead when its warm? And its only on #3?
Hrmmm, oddball. the crank sensor tells the plugs when to fire, the cam sensor (dizzy pickup) tells the injectors when to squirt. So the dizzy pickup (cam sensor) is one thing to consider. Other things would be looose connectors/bum injector wiring, flakey ECU (heat). Or just an out-of-spec injector.

I would test the dizzy pickup (cam sensor) first. And for sure I would do the mechanicals regardless.
.

hester88 · 04-25-2012, 05:47 AM

Yes. I started it up today while it was cold and idling fine and pulled cyl 3 injector plug and it affected the idle. Not a lot but it did affect it. Not really sure what that would mean. It doesn't affect it as much as cyl 4. I was thinking the same thing on maybe a bad wire and heating up making it loose connection. Tonight ill start it up and get it warm till it starts acting up and pull that connector off and see if it's getting power. Where is the dizzy pickup located? I was going to check the cam shaft sensor but when I looked it up the only replacement part I could find was crankshaft position sensor.